/*
 * @Author: Dagon
 * @Date: 2021-03-08 19:34:09
 * @Description: 
 */

var a = 3;
function change1(a) {
  a = 4
}
change1(a)
console.log(a) // 3

var user = { age: 30 }
function change2(user) {
  user.age = 40
}
change2(user)
console.log(user.age) // 40

function change3(user) {
  user = { age: 50 }
}
change3(user)
console.log(user.age) // 40